The invention relates to a control device operatively associated with a needle-bearing bar in a quilting machine. Such a device can be used in either quilting machines having a single needle-bearing bar or in quilting machines having a plurality of needle-bearing bars.
In the conventional quilting machines, the control device of the needle-bearing bar has driving means inserted between a main control shaft of the machine and the needle-bearing bar. These driving means are suitable to convert, via cam means, the rotatory motion of the main shaft into a reciprocating movement of the needle-bearing bar. Such conventional driving means forms a non-disengageable connection between the main shaft and the needle-bearing bar and does not permit a temporaneous stopping of the needle-bearing bar and, consequently, of the stitching operation. When the quilting machine is in operation, the needle-bearing bar is constantly in movement, and accomplishment of discontinuous quiltings, in order to manufacture quilted articles having stitched patterns with pattern-free zones intervening therebetween, is not readily possible. In order to obtain quiltings of the foregoing type, it has been necessary with the known machines to stop the entire combination of parts forming the driving means of the needle-bearing bar to cause thereafter the article being quilted to advance a predetermined length, and finally to restore the working of the combination of parts forming the driving means of the needle bearing bar. Obviously, such operations must be repeated whenever a non-stitched zone has to be prepared. This makes the working of the quilting machine extremely difficult and complex and, consequently, also the electric equipment provided for actuating, in timed coordination, the various operations. Machines of this type generally use, for the preparation of discontinuous stitchings, a self-braking motor which, whenever a stitch-free zone has to be prepared, must lock the main shaft of the machine and enable a secondary control device for moving the article which must advance without being stitched. The working complexity of the conventional machines results in the impossibility of increasing the production rate beyond a given limit; consequently, the output is necessarily limited. As a result, the manufactured articles are expensive. There should be also considered the possible frequent drawbacks which can occur, such as e.g. article tearing caused by the article advancement, if the needle-bearing bar is not at the top dead center, i.e. the needles are not in raised position with respect to the article.